Lake Wairarapa wetlands

Lake Wairarapa, Lake Onoke and their associated wetlands and scattered forest remnants are the largest wetland system in the lower North Island.

The area is considered to be of national and international importance for indigenous plant and animal communities.It is spiritually and traditionally important to Maori as an area for gathering such food as eel, fish, waterfowl, and plant material, including flax and raupo.

Lake Wairarapa wetlands

The Department of Conservation is working with iwi, other management agencies and stakeholders to restore wildlife habitat that has been degraded through human use. Agriculture and river development, flood control, and waterway diversions have resulted in the drainage of large areas of the wetlands, reducing their ecological values.

Wildlife

The diverse habitats within the wetlands attract a wide range of wetland birds, particularly to the lake’s eastern shore, a habitat of national importance for water and wader birds. Almost 100 bird species have been recorded there over the past two decades, including some international migratory birds.

Habitats include the open water of the lake; shallow water including backwaters; bare sandflats; marshlands including extensive areas of native turf and short rushes, open water in ponds, emergent swamp vegetation especially raupo, extensive areas of mingimingi (Coprosma propinqua) shrubs, and wetland forest dominated by introduced (exotic) willows.

Among the birds spotted in the wetlands are large numbers of bar-tailed godwit, golden plover, pied stilt, banded dotterel, black-fronted dotterel, great knot, Japanese Snipe and Caspian tern.

The wetlands are important breeding, feeding and roosting habitat for waterfowl, including grey duck, NZ shoveler, grey teal and paradise shelduck.

Three species of shag (black, little black and little pied), New Zealand dabchick, Australasian bittern, marsh crake and spotless crake also inhabit the wetlands.

Changes in the quality of the wetlands have led to the decline and even local extinction of some species (including fernbird) and an increase in others, such aspied stilt, mallard and paradise shelduck.

Lakes Wairarapa and Onoke and surrounding wetlands have also been identified as wetlands of national importance to fisheries. Among 10 native species which migrate between the sea and fresh water are long finned and short finned eel. The nationally threatened brown mudfish and giant kokopu have also been recorded in the wetlands.

Vegetation

The lake edge, which is regularly inundated by water and then exposed, supports a submerged “turf” community of small native plants which is greater in area than in any other North Island lake. Turf plants also grow on the edges of some of the ponds cut off from the main lake.

The nationally threatened mistletoe K. salicornioides grows on the western lake shore.

Scattered stands of kahikatea and cabbage trees and isolated totara, ribbonwood, kowhai and lacebark are remnants of the extensive areas of native forest that once existed in the area.

Today the wetlands are dominated by exotic forests comprising crack willow, hawthorn and alder. Growing among them are locally and nationally important natives -  the swamp stinging nettle (Urtica linearifolia) and a white flowering native violet (Viola lyalii)

The Lake Shore Scenic Reserve on the western shore is the last remaining area supporting the vegetation sequence that would have existed between the Rimutaka Range and Lake Wairarapa before agricultural development. It comprises a stand of mainly black beech, with some patches of titoki and karaka, and shrubs closer to the lake margin.

Much of the open lake water is devoid of aquatic vegetation, perhaps because of its high turbidity.

Hornwort at Lake Wairarapa

But the aquatic weeds hornwort and lagarosiphon have infested some of the ponds, threatening the ecological values of the area. Hornwort grows stems of up to six metres long, forming submerged “forests” and has the ability to spread rapidly and smother other species. Lagarosiphon, which also quickly spreads, has brittle stems up to a metre long, tiny pinkish flowers, and dark green leaves tapered to a sharp point.

People visiting the area are urged to prevent the spread of these weeds by washing down their boats and dogs after they’ve been in the water.

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